With reference to FIG. 6, a conventional guide tube (80) in accordance with the prior art is cylindrical and is used in a conventional protein skimmer. The conventional protein skimmer removes protein and suspended solids from aquarium water and has a basin (70), a foam generating assembly, a water valve (77), a guide tube (80), a mid cover (89) and a collecting assembly.
The basin (70) has a top, a circumferential wall, an inlet (72), an outlet (78) and a guide opening (79). The inlet (72) is formed through the top of the basin (70). The outlet (78) is formed through the circumferential wall of the basin (70). The guide opening (79) is formed through the top of the basin (70) near the inlet (72).
The foam generating assembly receives a flow of water contaminated with protein and suspended solids from an aquarium, injects minute bubbles into the flow of water, is connected to the inlet (72) of the basin (70) and has a connecting tube (76), a nozzle (74), an inlet tube (71), an air chamber (73) and an air valve (75). The connecting tube (76) has an outer end and an inner end. The outer end is connected to a submersible pump that pumps water from the aquarium into the connecting tube (76). The nozzle (74) is connected to the inner end of the connecting tube (76) and has a circumferential wall, an inner end and multiple air holes (741). The air holes (741) are formed through the circumferential wall of the nozzle (74) to allow air to pass into the nozzle (74) and mix with water in the nozzle (74) to generate the minute bubbles. Impurities suspended in the water, e.g. protein or other suspended particles adhere respectively to surface of the bubbles by surface tension of the bubbles and form foam that is carried with the water afflux.
The inlet tube (71) is connected to the outlet end of the nozzle (74) and has a bottom end. The bottom end of the inlet tube (71) is mounted in the inlet (72) in the upper wall of the basin (70) to allow the water containing the foam to pass into the basin (70).
The air chamber (73) is mounted around the nozzle (74), forms an airtight space around the air holes (741) in the nozzle (74) and has a circumferential wall and a mounting hole. The mounting hole is formed through the circumferential wall of the air chamber (73).
The air valve (75) is mounted in the mounting hole in the air chamber (73), is connected to an air pump, allows air to be pumped into the air chamber (73) and has a bottom end. The bottom end of the air valve (75) is mounted through the mounting hole in the air chamber (73) with an airtight fit such that air pumped into the air chamber (73) is sucked through the air holes (741) into the nozzle (74) by the water afflux passing through the nozzle (74) and is mixed with said water to form minute bubbles.
The water valve (77) is connected to the outlet (78) of the basin (70) to control the discharge of filtered water from the basin (70).
The guide tube (80) is cylindrical, is mounted on the upper wall of the basin (70), collects foam that rises from the basin (70) and has a lower end and an upper end. The lower end of the guide tube (80) is mounted in the guide opening (79) in the basin (70). Foam in the water in the basin (70) floats up through the guide opening (79) and accumulates in, fills and passes out of the upper end of the guide tube (80).
The mid cover (89) is mounted on the upper end of the guide tube (80) and has a mounting hole. The mounting hole is formed through the mid cover (89).
The collecting assembly is connected to the upper end of the vertical guide tube (80) and has an extension tube (83), a collection reservoir (82), a top cover (85) and a drain fitting (84). The extending tube (83) is smaller than the guide tube (80) and has a bottom end and an upper end. The bottom end of the extending tube (83) is mounted in the mounting hole in the mid cover (89), communicates with guide tube (80) and receives foam from the guide tube (80).
The collection reservoir (82) is mounted around the upper end section of the extending tube (83) and has an open top, a bottom, a circumferential wall and a drain hole. The drain hole is formed through the circumferential wall of the collection reservoir (82). The foam is continuously accumulated and rises until the foam spills out of the upper end of the extending tube (83) and settles in the collection reservoir (82). As the foam in the collection reservoir (82) transitions back to the water, impurities bonded to the foam are suspended in the water in the collection reservoir (82). Thus, impurities are filtered from the water and are collected in the collection reservoir (82).
The top cover (85) is mounted on the open top of the collection reservoir (82) and has an air hole. The air hole is formed through the top cover (85) to allow air released from the foam to escape.
The drain fitting (84) is mounted in the drain hole in the collection reservoir (82) to selectively draw off water and suspended impurities collected in the collection reservoir (82).
However, the mid cover (89) is backing up the foam in the guide tube (80) and causes most of the foam to collapse and reintroduce the impurities back into the water in the guide tube (80) and the basin (70) before the foam arrives at the upper end of the guide tube (80). Thus, the filtering efficiency of the conventional protein skimmer is reduced significantly.